Process for the production of lead glazes



Patented Aug. 2, 1938 y V UNITED STATES PATENTT'O'FFICE" Hermann Harkort, Berlin, Germany 'No Drawing. Application August 22, 1936, Serial No. 97,441. InSwitzerland August 26, 1935 7 Claims. (01. 1069362) This invention relates to a process for the In the presence of silicic acid, the metals deproduction of lead glaze, or glazing, which compose and reduce the sulphate which then, renders it pos t p u Such es 0 just as the oxidized reducing agent itself is conexcellent quality using initial materials which so verted-into lead silicate, or, in case of using, for far have been, considered as waste substances. instance, aluminum as the reducing agent, to Hitherto the lead has been, in most cases, inlead-aluminum silicate. Instead of the metals, t oduced into lead la P parations in the metal compounds may be used also, which are a form of litharge or red oxide of lead, (PbaOi) decomposed and oxidized by a reaction with-the (minium); sometimes also as white lead. or ingredients .of the preparation to be fritted,

0 ceruse, a lead preparation with a substantial and the. acid residue of which escapes from the content of basic lead carbonate, based on the preparation, while the metal is also combined presupposition that it is necessary for the producwith the glaze. after being oxidized by the retion of satisfactory glazes to use the initial sulting S03. H a materials in an accurately defined chemical As an initial material containing lead sul- 5 form, or degree of oxidation respectively. phate, leadslime is preferably .to be employed,

It has also already been suggested to use waste which is deposited in the casings of storagematerials of diiierent kinds with a lead content batteries as they are used up; of course, other or a n P rposes; however, these eXperimaterials containing lead sulphate may also be ments proved successful only if sulphate free used, such as roasted lead ores.

9 initial materials were used. When using initial These susbtances, more particularly the lead materials containing lead with more or less sulslime, besides lead sulphate also contain a subphate content, insurmountable difficulties have stantial percentage of lead oxide, the presence so far arisen, because the elimination of these of which neither hinders nor interferes with the sulphates, the existence of which, as is well process, but is, on the other hand, actually de- 5 known, causes the finished glaze to become sirable.

dull, was hardly possible by economical means. Again it proved to be very economical to use 011 the other hand just such substances conas a reducing agent a waste material rather than taining lead sulphate are cheaply available in pure metal dust, or pure material respectively. large quantities, and as waste or as intermediate A material of this kind, which is entirely suitable products in the treatment of lead ore. and available in large quantities, is the lead dust The difliculties presented by the use of such which occurs in the grinding of lead in drumsubstances containing sulphate are eliminated by, mills for the purposes of the storage battery the process according to the invention. This industry, and which is partially oxidized, but at success is attained by combining the initial matethe same time to such an extent that it is not 5 r a s Containing t e l d Su p in the p suitable for being employed in the production of tion or preparation to be fritted with inthe plate-filling paste. The content of lead gredients which decompose and reduce the suloxide, which on the one hand is detrimental to phates during the fritting, said material formthe proper purpose of the dust if exceeding cering simultaneously components of the glaze. tain well defined limits, is on the other hand Asareducing means introduced into the preparaadvantageous to the new process. It is merely tion to be fritted, beside the substances connecessary to consider on the one hand the sultaining lead sulphate, powderous metals which phate content of the lead slime, and on the are to be finely distributed in the preparation to other hand, the content of metallic lead in this be fritted, such as lead proper, or aluminum, are ground material in rating the percentages to be i used. These substances are introduced into the used.

p p ation to be fritted either singly, 0 Lead ash, (oxide of lead), such as obtained several simu ta s y, or e p tiv y in the in the melting, refining, or like treatments of form of a mixture, depending on the S03 almetallic lead as a waste material, may be used ready formed by the decomposition of the sulafter grinding as a decomposing agent with the l phate, or on the oxygen available accordingly, am ucces and in the amemann and accordi to thefollowing equation Practically the new process is realized in such Pbo S03 Pb +2 SZ-O2=2Pbo 81-02 302 a way that the above mentioned ingredients and the other substances of the glazing preparation and are mixed with one another in the corresponding i 3PbOSO3+2AL+4SO2=3PbO.AZ2O3.4SiO2+3SO2 percentages and then fritted. Under certain circumstances it is also possible to use the mixture of the ingredients without fritting, after the requisite grinding as a raw glaze; in which case, the mutual reaction of the ingredients takes place on ceramic body.

Taking as an example lead slime as an initial material 60% of which consists of PbSO4, a lead glazef can be made therefrom having the chemical structure of a lead mono-silicate having as its formula:

lPbOsiOz. starting from:

30% lead slime (from storage battery).

82% sand, and

62% ground and partially oxidized lead dust containing 20% metallic lead.

The application of the new process is not limited to the manufacture of lead glazes, but lead glass, enamel, and the like may also be produced by the same process.

Of course, if using partially oxidized lead dust, one can produce it especially for the purpose of the process according to the invention, instead of using waste material.

1. A process for producing lead glazes comprising the introduction of the lead into the preparation to be fritted in the form of a leadsulphate-containing substance, and the reduction of all of the sulphate during the fritting by means of a powderous metal which is combined with the glaze.

2. A process for producing lead glazes comprisingthe introduction of the lead into the composition to be fritted in the form of lead slime of the kind is deposited in the casings of storagebattery cells while in use, and the reduction of the sulphate contained in the lead slime during the fritting by means of a powderous metal which in that lead dust is used as a reducing agentl.

4. A process as claimed in claim 1, characterized in that aluminum dust is used as a reducing agent.

5. A process as claimed in claim 1, comprising the use of initial ingredients containing lead oxide.

6. A process for producing lead glaze, comprising the introduction of the lead into the preparation to be fritted in the form of a lead-sulphate-containing substance, and the decomposition of the lead-sulphate during the fritting by partially oxidized lead dust, such as is obtained when grinding lead in drum mills in the presence of air, the proportion of lead sulphate and the reducing metal used being such that all of the sullphate is converted finally into lead silicates by reaction with the silica present in the mixture.

'7. A process as claimed in claim 1, comprising 3 the use of a mixture of metallic lead and lead oxides, such as are formed as a by-product in the melting process of lead, as a reducing agent.

HERMANN HARKORT. 

